RO133216A2 - Microscope objective lens with automatic focusing - Google Patents

Abstract

The invention relates to a microscope objective lens with automatic focusing which enables a maximal depth optical resolution to be achieved using the controlled displacement of the focal point at various wave lengths of the focal line in the visible spectral range. According to the invention, the objective lens exhibits automatic adaptive optics comprising: a piezoelectric quartz actuator (3) which moves a concave mirror (6) or a convex mirror (7) to and from the analyzed matter (m), an image-acquisition optoelectronic system (d), a luminous intensity measuring optoelectronic system (e), a differential unit (f) for identification of focal points, a prescription and supply unit (g), a sensorial displacement control unit (h), an electronic computer (i) and a specialized software (j).

Description

MICROSCOPE OBJECTIVE WITH AUTOMOTIVE FOCUSING

The invention relates to an objective with adaptive optics for equipping reflection microscopes in order to increase their optical resolution at depth. Direct applications are in metallography, geology, forensics, chemistry, plastics, composites, biology, medicine, etc.

The quality of the image in the microscopes is given by the optical resolution whose value is maximum when the researched matter is located in the focal point of the optical focusing system, made in turn with groups of lenses or groups of metallic mirrors. The microscopic optical resolution is horizontal and deep and is defined as the minimum distance d [pm] between two points that can be clearly distinguished with the human eye by looking through the microscope's eyepieces or the image on a monitor obtained in turn through a camera. video mounted on the trinocular of the microscope:

<= 4 = - ^ - w

A n -ma where: λ - the wavelength of the light radiation used for irradiation of the investigated matter [pm] n - the refractive index of the transparent environment that is found between the researched matter and the lens of the microscope's optical lens a - the maximum half-radius formed by two radiations luminous starting from a point of the investigated matter and can still be caught by the edge of the lens focusing the optical lens of the microscope.

A-numerical aperture (J = w-sina)

By choosing transparent materials, located between the lens of focus of the optical objective of the microscope and the researched matter, having the refractive index greater than 1 (1 being the refractive index of the air) and the use of constructive solutions that allowed to reach an angle of 72 ° for the optical lens focusing lenses, the numerical aperture A has been brought to the maximum technically possible values. Until recently, the limit of optical zoom microscopes M was subject to the rule of Abbe [1] that, overall _max magnification M of a microscope must be between:

M _max = 500 Ar 1000A (2) to 2017 00661

15/09/2017 ^

Above this limit the image is blurred due to decreased optical resolution.

Because classical optical microscopes are based on light refraction, they have a horizontal optical resolution limited to half the wavelength of the radiation used to irradiate the investigated material. For the visible spectral domain this resolution corresponds to approx. 200 nm, which allows, according to Abbe's rule, to reach a magnification order M _max 1500 times for classical optical microscopy.

However, a focal lens does not have a focal point but has a focal line, and on this focal line there are hundreds of focal points, and each one corresponds to a certain wavelength (chromatic aberration) in the visible spectral range between 390 nm violet. and 780 nm - red, which is why a classic microscopic image is relatively low resolution.

An increase in the horizontal optical resolution d _y has been achieved by improving the chemical composition of the glass lens of the microscope objectives and by making convex and concave lens packages are stuck together. The result was the construction of achromatic, apochromatic and planapochromatic objectives. The former performs a chromatic correction for the median area of the visible spectrum (yellow-green area), and the latter for the entire area of the visible spectrum. However, the problem of optimum focal points has not been solved, these objectives only bring an improvement in the sense of mediating several wavelengths that they bring in a single focal point.

Depth resolution d _z is based on all the above definition, in that it represents the minimum distance at which two neighboring points can be clearly distinguished on the flank of a micrometric elevation. Ideally for an optical microscope, both horizontal resolution d _y and depth d _z will be maximum. However, these two important optical characteristics are antagonistic, the horizontal optical resolution d _y is antagonistic with the optical resolution at depth d _z , being linked by the relation:

d _v

-fi- = const (3) the attempt to increase the resolution at depth leads to the decrease of the resolution on the surface and vice versa. The reason is the fact that the horizontal resolution of the investigated matter is given by the numerical aperture A, that is, by the optical constructional characteristics of the focusing lenses and by the nature of the environment that is between the objective and the investigated material, while the depth resolution depends on the width of the spectral band. of the irradiation light of the investigated matter.

The maximum resolution when studying the microscopic details of the investigated matter is provided by the wavelengths that have values of the same order of magnitude with the microscopic details followed. Specifically, to obtain a maximum optical resolution of 2017 00661

15/09/2017 depth, for details of matter that varies within the wavelengths covered by the visible spectral domain (approx. 400nm), the microscopic image should be the result of an opto-electronic integration of several images obtained during the successive focusing. of all wavelengths in this spectral domain. In this way, the larger details on the depth of the roughness of the investigated material are reproduced with maximum optical resolution in the focal points of the red spectral domain, and the microscopic details of smaller dimensions are reproduced with maximum optical resolution in the focal points in the purple spectral domain.

The authors are familiar with autofocus solutions from the following documents:

Document Mr. titled: Lens drive device, camera module, and camera mounting devices, registered as TW201631348 (Aj-2016, describes an autofocus system using a linear electromagnetic coil actuator.

Document D2 entitled: Microscope Apparatus, Autofocus Apparatus, and Autofocus Method, registered as JP2017062438 (A) - 2017 describes a system of autofocus based on phase comparison of light radiation.

Document D3 entitled: Focus control device, Focus control Method, Focus control program, Lens device, registered as W02017057071 (A1) -2016, describes automatic focusing systems based on phase comparison of light radiation.

Document D4 TW 201632934 (Al) -2016 titled: The camera module autofocus, actuator and control method them, uses as an element of execution of the actuator an alloy wire with memory and an elastic element of return.

Also known are a variety of technical solutions used in high-performance cameras where through a control loop, which has as sensor a photoelectric detector and as an execution element an electric micromotor automatically changes the focal length of the lens group from the lens optical image of the camera so as to ensure the best optical resolution for an area of maximum interest in the image being viewed. The relatively large size of the servomotors that rotate in search of the optimum focus, the optical objective of the camera or linearly displaces, the group of lenses in the lens, in search of the optimum focus, either on the object in the foreground or in the background of the image, but especially the poor resolution of these servomechanisms. I make this solution inapplicable to Raman spectrometers. There are also known and used autofocus systems, made by interferometric means, on radio telescopes. Currently, by confocal microscopy but also by other solutions [2], [3], [4], [5] it was possible to increase the optical resolution at depth in a sensitive way and at microscopes. These achievements include state-of-the-art technical solutions, and microscopes are particularly expensive.

The technical problem to be solved by the invention consists in the achievement of an objective intended for reflection microscopes, which together with the associated microscopic and optoelectronic structure, allows to obtain a maximum optical resolution at depth through automatic focusing. For this purpose an adaptive optics is used which in fractions of a2017 00661

15/09/2017

second leads to the passage of dozens of focal points, located at the different wavelengths of the visible spectral domain, to the opto-electronic saving of microscopic images at these focal points as well as to the reproduction of these images as 3D surface tomograms or as dynamic trains of successive microscopic images. Industrially, the microscope objective according to the invention together with the related optoelectronics may be implemented on a new generation of microscopes or may be used to transform classical reflection optical microscopes into high resolution optical microscopes at depth.

The technical embodiments of the invention start from the idea that the only way to improve the optical resolution at depth is to exploit the entire spectral band in the visible field to obtain a high resolution microscopic image. The relationship that defines the optical resolution in this case is as follows:

¹ To n (4)

In this relation, the homologue to the relation (1), R _o represents the optical resolution, and the factor k represents a subunit coefficient, which is even smaller as a microscope with an objective with active optics manages to position the focal point at lengths. wave as close as possible to each other.

In order to materialize the invention, the authors describe a microscope objective with active microscope optics, in three conceptual and constructive variants, possible to achieve industrially. In order to be free of chromatic aberrations and to benefit from the entire spectrum from ultraviolet to infrared, two silver mirrors, one concave and one convex, are used in the construction of microscope targets instead of the classic apochromatic or planapochromatic focus lenses. for maximum depth resolution, they have a piezoelectric actuator with parallel planar faces. To ensure high reproducibility, the piezoelectric actuator oscillates on the resonant frequency f _r :

(5) where: I - thickness of piezoelectric quartz plate p - density of quartz

E- the modulus of elasticity of the quartz

The recommended resonance frequency value f _r is 0.1 MHz. At this frequency are possible thicknesses of the quartz disk, from the composition of the piezoelectric actuator, of the order of millimeters and its expansion-contraction displacements of about 1000 nm, of 2017 00661

15/09/201 which covers reaching the wavelengths for all focal points in the visible spectral domain. Over the high-frequency supply voltage, which maintains the quartz disk of the piezoelectric actuator at the stable resonant frequency, DC voltage stages are superimposed, obtained with an electronic generator that cyclically produces increasing electrical voltages followed by electrical voltage steps. descending of the same value. The increasing voltage steps cause, in proportion to the applied voltage, the expansion of the piezoelectric actuator with a precise increase, by the order of nanometers, and the decreasing voltage steps cause its contraction with the same increase of the order of the nanometers, (Fig.l). Correspondingly with these expansions and contractions, the axial displacement, with the same precise incremental steps, of one of the two metal mirrors towards the other and from the other is realized. In this way, the focal points corresponding to the different wavelengths on the focal line characteristic to the visible spectrum between 390-780 nm are accessed. The control of the level of axial displacement caused by the piezoelectric actuator is performed, according to the solution of the invention, with the help of a capacitive sensor, made in the form of parallel planar reinforcements of the capacitor, placed between the piezoelectric actuator and the upper body on one of the constructive variants, respectively between the piezoelectric actuator and the support with three arms on the lower body of the optical microscope lens, (Fig.3), (Fig.4) and (Fig.5). At each precise incremental step of moving one of the two mirrors of the optical lens, a focal point and a corresponding microscopic image acquisition are automatically achieved. Prescribing the step of the wavelengths where focal points need to be made is made by the operator. The control and validation of the attainment of that of a focal point, is established by a differential unit that continuously compares the level of displacement of one of the two focusing metal mirrors, level given by the capacitive sensor signal, with the level of an electrical signal given by a CCD type sensor, which sets the maximum intensity of a light beam deflected with an optical prism from the reflected light beam from the investigated matter. The precise detection of reaching the maximum intensity of the light radiation is realized by the specialized software that uses for this purpose the zero value of the derivative of the luminous intensity (/) depending on the time (t):

(6)

The zero value of a derivative always shows the attainment of a maximum or a minimum, in the concrete case it shows the attainment of the focal point. All these operations are managed by an electronic computer, through specialized software, which also ensures the processing of the package of images acquired during the scanning of the piezoelectric actuator, to be played either as 3-D tomograms or as image by image at a speed set by the researcher.

By applying the invention, the following advantage is obtained:

to 2017 00661

15/09/2017 ^

The use of adaptive optics, made with a piezoelectric actuator of quartz, noninertial, non-frictional games, without friction, with high dynamics and reproducibility, allows the precise and extremely fast displacement of the focal point of the polychromatic radiation in the field. spectrally visible at different wavelengths and thereby creates a powerful means of improving, measuring and controlling the optical resolution at depth. The result of applying the solution according to the invention is obtaining and storing, in fractions of a second, a high resolution microscopic image package, each of these images corresponding to another focal point and to another wavelength. The package of microscopic images acquired by optoelectronic means can be reproduced, either in the form of 3-D tomograms or in the form of an image train, which runs successively on the monitor, at a speed regulated by the researcher, by means of specialized software.

The following are three examples of embodiments of the invention in connection with FIG. Fig. 2; Fig. 3; Figure 4; Fig. 5; Fig.6; which represents: Fig.l- Principle diagram of the autofocus microscope objective

Fig.2 - The modular structure of an optical microscope equipped with an autofocus lens

Fig.3- Optical scheme of principle of the autofocus microscope objective obtained by moving the concave mirror

Fig. 4 - Constructive variant for the autofocus microscope lens that uses the concave mirror displacement

Fig. 5 - Constructive variant for the autofocus microscope lens that uses the displacement of the convex mirror

Fig.6- Constructive variant of autofocus having the focal point search optoelectronics integrated in the optical objective of the microscope

A microscope (Fig2) which uses for the study of the subject m investigated an optical lens with autofocus according to the invention also has in its structure an optical tube b, a trinocular optical unit, an optoelectronic image acquisition system, an optoelectronic imaging system. measurement of the luminous intensity of the visible spectral domain, a unit f differential search for focal points, a unit g of prescription and supply with electrical voltages in stages, a sensorial unit h of control of movement, a computer / electronic and a specialized software j .

For the microscope objective of autofocus, which is the object of the invention, three conceptual and constructive variants are presented as follows:

1. Microscope objective with controlled displacement of the concave mirror

2. Microscope objective with controlled displacement of the convex mirror

3. Microscope lens with integrated optoelectronics

The microscope objective with the controlled displacement of the concave mirror (Fig.3), (Fig.4), is composed of an upper body 1, a lower body 2, a piezoelectric actuator 3 with plane-parallel faces and a central circular hole, a capacitive displacement sensor a2017 00661 format

09/15/2017 from two fittings 4 and 5 parallel plane of capacitor provided with a central orifice, a mirror 6 concave, a mirror 7 convex, a support 8 with fixation by three arms and an electrical connector 9.

The objective of the microscope with the controlled displacement of the convex mirror. (Fig. 5) is composed of an upper body 10, a lower body 11, a piezoelectric actuator 12 with parallel-plane faces, a capacitive displacement sensor consisting of two reinforcements 13 and 4 parallel plane capacitors, a mirror 6 concave, a mirror 7 convex, a support 8 with three-arm mounting and an electrical connector 15.

The microscope lens with integrated optoelectronics focusing focal point (Fig. 6), is composed of an upper body 16, a lower body 11, a piezo-electric actuator 12 with parallel-plane faces, a capacitive displacement sensor consisting of two reinforcements 13sil4 of parallel plane capacitor, a mirror 6 concave, a mirror 7 convex, a support 8 with three-arm mounting and an electrical connector 15. The composition of this type of lens also includes an optoelectronic module A composed of a cylindrical body 17 on which is mounted externally an optical prism 18, and inside two disks 19 and 20 with circular slots, a group 21 of lenses. collimators, an optical detector 22 of CCD type and a screw 23 for centering and fixing the optoelectronic module A. The connection of the optoelectronic module A with the optoelectronic system for the search of focal points is achieved through an electrical connector 24. The role of optoelectronic module A is to divert 90% of the light beam reflected from the subject m investigated to the 22 CCD detector whose signal is used by the optoelectronic focal point search system to correlate the wavelength of a particular focal point on the spectral line of the visible field with the microscopic image saved for that focal point.

to 2017 00661

09/15/2017 3S

BIBLIOGRAPHY

1. Schumann Herman, Metallographie, VEB Deutscher Verlag ftir Grundstoffindustrie Leipzig, 1974,

2. Harry Paul, Lexikon der Optik. Spectrum Akademischer Verlag, 2003, ISBN 3-8274-1422-9.

3. [https://de.wikipedia.org/wiki/Optische_Koh%C3%A4renztomografie]

4. Ștefan Hippler, Adaptive Optics, Der scharfe Blick ins AII und ins Auge, Phys. The nserer Zeit, 36. Jahrgang, Nr. 1, 2005, D0l: 10.1002 / piuz.200501055 © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

5. Douglas B. Murphy, Fundamentals of Light Microscopy and Electronic Imaging, WileyLiss, Inc.2001

Claims (11)

1. The invention Self-focusing microscope objective, characterized in that, in order to obtain a maximum depth resolution at reflection optical microscopes, a microscope objective is presented, presented in three constructive variants, which consists of an auto-formed active optic. in turn, of some piezoelectric actuators (3) and (12), some fittings (4), (5), (13) and (14) of capacitors, a concave mirror (6), a convex mirror (7), a optoelectronic system (s) for measuring light intensity, a differential focal point search unit (s), a prescribing and supply unit (g), a sensory displacement control unit (h), an electronic computer (/) and specialized software (/). 2. Autofocus microscope objective according to claim No. 1, characterized in that, in order to cover without chromatic aberrations the entire visible spectral range between 390 nm and 780 nm, for all three constructive variants of autofocus optical lenses. according to the invention, a concave mirror (6) and a silver convex mirror (7) are vacuum-deposited on the surface of the respective convexity of the mirror body; 4. Microscope objective with controlled displacement of the concave mirror, according to Claim No. 1, and Claim No. 2, characterized in that the modification of the focal length, in order to ensure a high optical resolution, a high image acquisition speed due to the lack of mechanical inertia and friction, it is achieved by moving the concave mirror (6), towards and from the convex mirror (7), using a quartz piezoelectric actuator (3) mounted between the upper body (1) and the mirror (6). ) concave, the actuator having the shape of a disc with parallel plane faces with a central circular orifice through which the light radiation falls on the investigated matter (m) from where it returns in the form of radiation reflected in the optoelectronic (/) system for searching the focal points in the field spectrally visible also at the (d) optoelectronic image acquisition system; 5. Microscope objective with the controlled displacement of the convex mirror according to Claim No. 1 and Claim No. 2, characterized in that the modification of the focal length, in order to ensure a high optical resolution, a high image acquisition speed under the conditions lack of mechanical inertia and friction, is achieved by moving the convex mirror (7), towards and from the concave mirror (6), using a quartz piezoelectric actuator (12), in the form of a full disk with parallel plane faces, mounted between the support (8) with three-arm fastening and the mirror (7) convex; to 2017 00661 09/15/2018 ^ 6. Integrated optoelectron microscope lens according to Claim No. 1, Claim No. 2 and Claim No. 5, characterized in that, in order to be mounted on any existing reflection microscope, this type of lens has a unitary optoelectronic module (A) mounted inside the upper body (16), comprising a cylindrical body (17), on which an optical prism (18) is mounted externally, and inside two discs (19) and (20) with circular slots, a group of lenses (21) collimators and a detector (22) CCD, the module (A) being centered and rigidized on the upper body (16) of the optical lens with a screw (23) drowned; 7. Differential focal point search unit (/), according to claim No. 1, characterized in that, in order to reach the focal point of a certain wavelength in the visible spectral domain and to achieve the acquisition and storage of the microscopic image exactly in this instead, a differential unit (/) is used, in which the values of the voltage stages applied to the piezoelectric actuators by the step-unit (g) are compared with the values of the voltages which correspond to the maximum intensity of the reflected light radiation (contrast) provided by the system (s). ) optoelectronic for measuring the luminous intensity of the visible spectral domain and the signal values of the capacitive sensor of the movement control unit (h); 8. Prescription power supply unit (g) in step according to Claim No. 7 and Claim No. 7, characterized in that it supplies the piezoelectric actuators (3) and (12), which in turn causes the controlled incremental displacement of the concave mirror (4) or causes the incremental controlled displacement of the convex mirror (7), this unit is in turn controlled by the differential (/) unit of search for focal points in the visible spectral domain, of the computer (/ ) electronic and specialized software (/); 9. Sensory movement control unit (h), according to Claim No. 1, of Claim No. 7 and Claim No. 8, characterized in that, in order to measure the actual displacement of the piezoelectric actuators (3) and (12) supplied by the supply unit (g), a capacitive sensory system composed of some reinforcements (4), (5), ( 13) and (14) of the capacitor, mounted between the piezoelectric actuators (3) and (12) and the bodies (l) and (ll), corresponding to the three constructive variants of the self-focusing microscope optical objectives, described; 10. Optoelectronic system (s) for measuring the light intensity in the visible spectral range, according to claim No. 1 and claim No. 7, characterized in that it comprises the optoelectronic module (A) formed in turn from a cylindrical body (17) on which an optical prism (18) is mounted externally, and inside are mounted two discs (19) and (20) with circular slots, a group (21) of collimating lenses, a 2017 00661 detector 09/15/2017 / p (22) optical type CCD and a screw (23) for centering and fixing the optoelectronic module (A) in the upper body (16); 11. Optoelectronic system for determining the maximum luminous intensity in the visible spectral domain, according to Claim No. OO, characterized in that the detection of the maximum intensity of the luminous radiation, which always corresponds to reaching the focal point, is made by the derivative of the intensity / of the radiation reflected from the subject (m) studied as a function of time t, a derivative that always has a maximum value of zero, as well as with the help of specialized software, which through the optoelectronic imaging system (d) and the computer ( /) electronically controls the acquisition and storage of the microscopic image when the derivative reaches zero; 12. Surface and succession tomography of microscopic images according to claim No. 1, characterized in that, by means of a specialized software (/) and an electronic computer (s), they can be rendered either in the form of a 3D microscopic image of tomogram type, either in the form of dynamic image processing, with a rate of 1- 60 images per second.